In a cellular wireless communication system, a service area is divided into no less than two cells and a radio base station is installed in each cell to realize the wireless communication. It is necessary in order to secure an enough high quality of communication in the service area to carry out properly a layout of base stations and an adjustment of wireless parameters such as directions of antennas, tilt angles of antennas and antenna powers considering surroundings such as geographical features, a building distribution, and a user distribution. A radio wave propagation simulator is applied in general as a means to support the area design.
A radio wave propagation simulator estimates a plane distribution condition of radio wave quality such as a Received Signal Code Power (RSCP) and a ratio of energy per chip of a desired wave to in-band received power density (Ec/NO) based on a base station information (location of the base station and wireless parameters), a map information, a building information and so on, around the area of design target area. As typical techniques for the radio wave propagation estimation, the following techniques are well known; statistical techniques such as the Hata/Okumura model in which a propagation curve showing radio wave propagation characteristics is statistically modeled based on actual measured data of radio wave quality, and the ray tracing method in which radio wave propagation characteristics are predicted in a determinism way by geometric optics techniques.
Several technical methods are proposed in order to improve accuracy of radio wave propagation estimation because the difference between an estimated radio wave quality and an actual radio wave quality is an important problem in the area design using a radio wave propagation simulator.
For example, a method (refer to patent document 1) to revise the above mentioned propagation curve used in a statistical technique based on an actually measured radio wave quality (actual measured data) in the area, and a method (refer to patent document 2) to estimate a radio wave building penetrating loss which causes errors in radio wave propagation estimation based on land utilization data and data of the number of households are given. As a method to get an actual measured data of radio wave quality, such a technology is also proposed as to acquire location information where communication quality deterioration occurred and quality deterioration information with applying mobile terminals actually used by users (refer to patent document 3).
Patent document 1: Japanese patent Laid-open publication No. 2005-223732 (Japanese patent No. 3862021)
Patent document 2: Japanese patent Laid-open publication No. 2002-016556 (Japanese patent No. 3403701)
Patent document 3: Japanese patent Laid-open publication No. 2002-271833